NAME

       truncate, ftruncate — truncate or extend a file to a specified length

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <unistd.h>

       int
       truncate(const char *path, off_t length);

       int
       ftruncate(int fd, off_t length);

DESCRIPTION

       The  truncate() system call causes the file named by path or referenced by fd to be truncated or extended
       to length bytes in size.  If the file was larger than this size, the extra data is lost.  If the file was
       smaller than this size, it will be extended as if by writing bytes with the value zero.

       The ftruncate() system call causes the file or shared memory object backing the file descriptor fd to  be
       truncated  or extended to length bytes in size.  The file descriptor must be a valid file descriptor open
       for writing.  The file position pointer associated with the file descriptor fd will not be modified.

RETURN VALUES

       Upon successful completion, the value 0 is returned; otherwise the value -1 is returned  and  the  global
       variable  errno is set to indicate the error.  If the file to be modified is not a directory or a regular
       file, the truncate() call has no effect and returns the value 0.

ERRORS

       The truncate() system call succeeds unless:

       [ENOTDIR]          A component of the path prefix is not a directory.

       [ENAMETOOLONG]     A component of a pathname exceeded 255 characters, or an  entire  path  name  exceeded
                          1023 characters.

       [ENOENT]           The named file does not exist.

       [EACCES]           Search permission is denied for a component of the path prefix.

       [EACCES]           The named file is not writable by the user.

       [ELOOP]            Too many symbolic links were encountered in translating the pathname.

       [EPERM]            The  named  file  has its immutable or append-only flag set, see the chflags(2) manual
                          page for more information.

       [EISDIR]           The named file is a directory.

       [EROFS]            The named file resides on a read-only file system.

       [ETXTBSY]          The file is a pure procedure (shared text) file that is being executed.

       [EFBIG]            The length argument was greater than the maximum file size.

       [EINVAL]           The length argument was less than 0.

       [EIO]              An I/O error occurred updating the inode.

       [EINTEGRITY]       Corrupted data was detected while reading from the file system.

       [EFAULT]           The path argument points outside the process's allocated address space.

       The ftruncate() system call succeeds unless:

       [EBADF]            The fd argument is not a valid descriptor.

       [EINVAL]           The fd argument references a file descriptor that is not  a  regular  file  or  shared
                          memory object.

       [EINVAL]           The fd descriptor is not open for writing.

SEE ALSO

       chflags(2), open(2), shm_open(2)

HISTORY

       The truncate() and ftruncate() system calls appeared in 4.2BSD.

BUGS

       These calls should be generalized to allow ranges of bytes in a file to be discarded.

       Use of truncate() to extend a file is not portable.

Debian                                           March 30, 2020                                      TRUNCATE(2)